For example, a separator of a fuel cell forms a reaction gas passage, and functions as a conductor for supplying an electric current generated by contacting with an electrode to the outside, and it is hence required to be low in contact resistance. Recently, from the viewpoint of strength and corrosion resistance, fuel cell separators made of stainless steel are drawing attention. Stainless steel products are superior in corrosion resistance because a passive film is formed on the surface; however, the passive film is high in electrical resistance. Accordingly, in Japanese Patent Application Laid-open (JP-A) No. 10-228914, it is proposed to reduce the electrical resistance by plating the separator contact area with gold.
In this proposal, however, because of gold plating, the separator becomes very expensive, and the manufacturing cost of the fuel cells is higher. In JP-A No. 11-121018, a separator having carbon particles buried in the surface of a stainless steel product is proposed. However, this separator easily falls off due to friction caused by vibration or the like, and is not suitable for long-term use.